Which version of extensible hypertext markup language (xhtml) is not backward compatible with html? a. true b. false questions?

XHTML stands for EXtensible HyperText Markup Language. It is almost identical to HTML, but is stricter than HTML. XHTML is HTML defined as an XML application and it is supported by all major browsers. The version of extensible hypertext markup language (XHTML) v 2.0 is not backward compatible with HTML. 

Hypothesis: volumes of both figures are equal.the volume of  figure 1 is: .the volume of figure 2 is: .since , you can conclude that and . so, .volumes of figures are equal only when an angle in the basis is right (then figures will be the same), in another cases volume of figure 1 is less than volume of figure 2.the hypothesis was not correct in all cases.